1. Field of the Invention
This invention relates to a method and system apparatus , and in particular to a control to limit millicode routing end branch prediction.
2. Description of Background
Prior work includes applications assigned to IBM which include:
U.S. Published Patent Application US20090217002A1: SYSTEM AND METHOD FOR PROVIDING ASYNCHRONOUS DYNAMIC MILLICODE ENTRY PREDICTION, filed by James J. Bonanno, et al. on Feb. 21, 2008, which relates to: a system and method for asynchronous dynamic millicode entry prediction in a processor are provided. The system includes a branch target buffer (BTB) to hold branch information. The branch information includes: a branch type indicating that the branch represents a millicode entry (mcentry) instruction targeting a millicode subroutine, and an instruction length code (ILC) associated with the mcentry instruction. The system also includes search logic to perform a method. The method includes locating a branch address in the BTB for the mcentry instruction targeting the millicode subroutine, and determining a return address to return from the millicode subroutine as a function of the instruction address of the mcentry instruction and the ILC. The system further includes instruction fetch controls to fetch instructions of the millicode subroutine asynchronous to the search logic. The search logic may also operate asynchronous with respect to an instruction decode unit; and
U.S. Published Patent Application US20090217016A1: SYSTEM AND METHOD FOR SEARCH AREA CONFINED BRANCH PREDICTION, filed by James J. Bonanno et al., Feb. 22, 2008, which relates to a system and method for performing search area confined branch prediction in a processor. The system includes a branch target buffer (BTB) to hold branch information for branch prediction, where the branch information includes a branch address. The system also includes search logic for searching the BTB to locate a branch address. The system additionally includes throttle logic to stop searching the BTB in response to reaching a predefined search limit.